v1.5.4 breaks generated jsonb default value for postgres

## Description

I'm using gorm.io/gen to generate models from schema. Driver update from v1.5.3 to v1.5.4 changed the way default value for jsonb is generated.

```go
// v1.5.3
type MyModel struct {
Data datatypes.JSON `gorm:"column:data;type:jsonb;default:'{}'" json:"data"`
}

// v1.5.4
type MyModel struct {
Data datatypes.JSON `gorm:"column:data;type:jsonb;default:{}" json:"data"`
}
```
(datatypes.JSON is my customization with DataTypeMap)

Now when running `AutoMigrate` I get the following error:
```
Error migrating the database: ERROR: syntax error at or near "{" (SQLSTATE 42601)
```